Start by melting your butter in a medium saucepan over medium heat. Stir constantly to ensure it doesn’t burn. Soon, it will turn golden brown, releasing a rich, nutty scent that’s absolutely irresistible. Remove from heat and let the butter cool for about 10 minutes before adding it to the rest of your ingredients.
In a separate bowl, whisk together the flour, baking soda, and salt. In a large bowl, combine the cooled brown butter with the dark brown sugar and granulated sugar. Beat until the mixture is smooth and slightly fluffy.
Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract. Gradually fold in the dry ingredients, just until combined.
Gently fold in the semi-sweet chocolate chips and any optional dark chocolate chunks. Chill the dough for 30 minutes to 24 hours if you want thicker cookies.
Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper. Scoop dough balls onto the sheet, spacing them about 2 inches apart. Bake for 10–12 minutes, until the edges are golden brown and the centers remain soft.
If you like a sweet-and-salty contrast, sprinkle a few sea salt flakes on each warm cookie. Let them cool on the baking sheet for 5 minutes, then transfer to a wire rack.